Field of the Invention
The present invention relates to a display device, and more particularly, to a timing controller, a driving method thereof, and a display device using the same, which can solve an image-sticking problem.
Discussion of the Related Art
Flat panel display (FPD) devices are applied to various electronic devices such as portable phones, tablet personal computers (PCs), notebook computers, etc. The FPD devices include liquid crystal display (LCD) devices, plasma display panels (PDPs), organic light-emitting display devices, etc. Recently, electrophoretic display (EPD) devices are widely used as the FPD devices.
Among such display devices, organic light-emitting display devices use a plurality of self-emitting elements that self-emit light, and thus have a fast response time, a high emission efficiency, a high brightness, and a wide viewing angle.
FIG. 1 is a graph showing an example of a method in which luminance is reduced with time in a related art organic light emitting display device, FIG. 2 is a flowchart illustrating a related art method of reducing luminance with time, and FIG. 3 are exemplary diagrams illustrating images having the same total average luminance when applying the related art method of reducing luminance with time.
Each of a plurality of pixels of a general organic light emitting display device includes an organic light emitting diode (OLED) and at least two or more transistors (T1, T2) that are connected to a data line (DL) and a gate line (GL) to control the organic light emitting diode (OLED).
The organic light emitting display device uses the organic light emitting diode (OLED) that is a self-emitting element, and thus has higher power consumption than other types of display devices.
The organic light emitting display device, as shown in FIGS. 1 and 2, uses a method of reducing luminance with time, for decreasing power consumption.
The method of reducing luminance with time gradually reduces luminance of a still image with time, and FIG. 1 shows an example that reduces the luminance of the still image with time.
The related art method of reducing luminance with time, as illustrated in FIG. 2, inputs an image in operation S10, and determines whether the input image is a still image in operation S20. When it is determined that the input image is not a still image, the related art method outputs the original image as-is in operation S40, and when it is determined that the input image is the still image, the related art method reduces luminance with time in operation S30, and outputs the image with reduced luminance in operation S40.
As described above, technology for temporally reducing luminance of a still image should preferentially perform an operation that determines whether a currently output image is a still image.
Generally, when frames having the same average grayscale level (APL) of an image are continuously input for a certain time or more, a current image is determined as a still image.
However, a method that determines whether a current image is a still image by using an average grayscale level (APL) of an image has a limitation.
For example, in FIG. 3, two images (frames) having the same average grayscale level (APL) are illustrated. When intuitively seen, an image illustrated in a portion (a) of FIG. 3 is not similar to an image illustrated in a portion (b) of FIG. 3.
However, the related art technology determines whether a current image is a still image by using an average grayscale level (APL), and thus, although two images of FIG. 3 are not still images, the related art technology determines the two images of FIG. 3 as still images and reduces luminance. That is, the related art technology reduces luminance of an image that is not a still image.
Moreover, since the related art technology reduces luminance of only a still image, the related art technology cannot greatly contribute to decrease power consumption of the organic light emitting display device. This is because cases of continuously viewing a still image are very rare under a viewing environment of general display devices.
The related art technology has the following problems.
First, since the related art technology determines whether a current image is a still image by using an average grayscale level (APL) and then reduces luminance of the still image, luminance of an image that is determined as not being the still image can be reduced.
Second, since the related art technology reduces luminance of only a still image, a reduction efficiency of power consumption is not high under a viewing environment of general display devices.